The present invention relates to a motor control apparatus and a power steering apparatus.
Japanese Patent Application Public Disclosure No. 2001-327173 (hereinafter referred to as a patent document 1) discloses an example of this technique. The patent document 1 discloses an invention that detects a current value of each phase by detecting a current passing through a direct-current bus. At this time, this invention increases an instruction voltage value of a maximum phase instruction voltage value in a first half of a PWM cycle by a correction amount set according to a difference between the maximum phase instruction voltage value and a middle phase instruction voltage value, and reduces an instruction voltage value in a second half of the PWM cycle by the correction amount corresponding to the previous increase, when the difference between the maximum phase instruction voltage value and the middle phase instruction voltage value (a second phase instruction voltage value) is smaller than a predetermined value. Further, the invention reduces an instruction voltage value of a minimum phase instruction voltage value in the first half of the PWM cycle by a correction amount set according to a difference between the middle phase instruction voltage value and the minimum phase instruction voltage value, and increases an instruction voltage value in the second half of the PWM cycle by the correction amount corresponding to the previous reduction, when the difference between the middle phase instruction voltage value and the minimum phase instruction voltage value is smaller than a predetermined value. Hereinafter, this correction will be referred to as a pulse shift.
According to the technique discussed in the patent document 1, the voltage of the phase on which the pulse shift is performed reduces instantaneously when the instruction voltage value is corrected downwardly, and increases instantaneously when the instruction voltage value is corrected upwardly, resulting in generation of a current ripple. At this time, the current ripple is generated around a voltage value different from a sum of the instruction voltage values of the respective phases, thereby leading to a possibility of a reduction in accuracy of current detection.